If you're looking for love on Valentine's Day, you may want to skip your e-mail — it could end up giving your computer a nasty virus.

At least two spam e-mails that disguise themselves as Valentine's Day greetings are making the rounds on the internet, threatening to hijack PCs that run on the Microsoft Windows operating system or steal online banking information from them, internet and computer security companies warned Wednesday.

One of the spam messages carries a worm that tries to send itself to e-mail addresses found on an infected computer once a person clicks on an attached file to open it, Sophos PLC of Abingdon, England, reported Wednesday.

Worms are self-replicating computer viruses that do not need to use another program to function, and don't always need people to activate them.

The spam e-mail subject lines are all related to Valentine's Day, Sophos said.

The company's researchers think that in addition to trying to e-mail itself to other computers, the W32/Dref-AB worm tries to download additional malicious code from the internet and turn infected PCs into part of a zombie network, which it then uses to send spam for hacking gangs.

Zombies are computers that have been infected by a virus that makes them automatically churn out spam or malware. They often send out viruses that turn other computers into part of a spam network.

"Cynical hackers are using the theme of Valentine's Day to conquer innocent people's computers and use them for their own money-making purposes," Sophos senior technology consultant Graham Cluley said in a written statement.

Sophos said the worm was responsible for about three-quarters of the threats it was seeing on Valentine's Day.

Spam lures victims to download Trojan

Another spam e-mail disguised as a Valentine's Day card is circulating around the internet, a Helsinki-based internet and security company warned Wednesday.

The e-mail hides a Trojan that creates files in the Windows system directory and attempts to steal online banking information such as login names, passwords, personal identification numbers and more, F-Secure Corp. said in a post on its security lab blog.

When a person clicks on a link in the e-mail, it opens a web page that asks the user to install Adobe Systems Inc.'s Flash Player. The Flash file format is commonly used by electronic greeting card websites.

Clicking the link for the false player actually downloads a Trojan, a program that appears to do one thing but hides another, usually malicious function. F-Secure calls the Trojan BZub.

F-Secure's software is identifying the malicious files being propagated through the e-mailed web link as Valenvir.A and BZub.HZ.

People can block the threat posed by Trojans by updating antivirus and other security software.

Users of computers made by Apple Inc. that run versions of the Mac operating system are not affected by either of the viruses.